Internally cooled airfoil

ABSTRACT

A casting core and/or an airfoil may comprise a tip flag cavity having a forward pedestal and a first spear pedestal disposed aft of the forward pedestal. A trailing edge discharge cavity may be separated from the tip flag cavity and include a first row of pedestals. The first row of pedestals may comprise a first racetrack pedestal. A second row of pedestals may be disposed aft of the first row of pedestals and include a second racetrack pedestal. A third row of pedestals may be disposed aft of the second row of pedestals and include a circular pedestal. A fourth row of pedestals may be disposed aft of the third row of pedestals and include a second spear pedestal.

FIELD

The disclosure relates generally to gas turbine engines, and moreparticularly to an airfoil having internal cooling features.

BACKGROUND

In the pursuit of ever higher efficiencies, gas turbine manufacturershave long relied on higher and higher turbine inlet temperatures toprovide boosts to overall engine performance. In typical modern engineapplications, the gas path temperatures within the turbine exceed themelting point of the component constituent materials. To combat thedemanding temperatures, dedicated cooling air may be extracted from thecompressor and used to cool the gas path components, incurringsignificant cycle penalties. Cooled components may include, for example,rotating blades and stator vanes in the turbine.

One mechanism used to cool turbine airfoils includes utilizing internalcooling circuits and/or a baffle. Typically, numerous film cooling holesand high volumes of cooling fluid are used to provide airfoil cooling.To augment the internal cooling, a number of interior treatments to thepassages have been implemented including pedestals, air jet impingement,and turbulator treatments for the walls. These internal cooling featuresare typically made by casting with the cores defining the internalfeatures. More intricate cores typically result in higher manufacturingcosts.

SUMMARY

A casting core is provided. The casting core may comprise a tip flagcavity having a forward pedestal and a first spear pedestal disposed aftof the forward pedestal. A trailing edge discharge cavity may beseparated from the tip flag cavity and include a first row of pedestals.The first row of pedestals may comprise a first racetrack pedestal. Asecond row of pedestals may be disposed aft of the first row ofpedestals and include a second racetrack pedestal. A third row ofpedestals may be disposed aft of the second row of pedestals and includea circular pedestal. A fourth row of pedestals may be disposed aft ofthe third row of pedestals and include a second spear pedestal.

In various embodiments, a diameter of the first racetrack pedestal maybe equal to a diameter of the second racetrack pedestal. A diameter ofthe spear pedestal may be greater than the diameter of the firstracetrack pedestal. The diameter of the spear pedestal may be, forexample, 0.026 inches. The first row of pedestals may have 12 racetrackpedestals, and the fourth row of pedestals may have 24 spear pedestals.The first row of pedestals may have a blockage of 71%.

The second row of pedestals may have a blockage of 71%. The blockage ofthe third row of pedestals may be 51%, and the blockage of the fourthrow may be 51%. A diameter of the forward pedestal may be equal to adiameter of the circular pedestal. The geometry of the first spearpedestal may be the same as the geometry of the second spear pedestal.The first row of pedestals may also be staggered relative to the secondrow of pedestals. The first spear pedestal may include a first depth andthe second spear pedestal may include a second depth less than the firstdepth. The first depth may be, for example, 0.020 inches and the seconddepth may be 0.012 inches.

An airfoil is also provided. The airfoil may include comprise a tip flagcavity having a forward pedestal and a first spear pedestal disposed aftof the forward pedestal. A forward internal cavity may be configured toprovide cooling fluid to the tip flag cavity. A trailing edge dischargecavity may be separated from the tip flag cavity and include a first rowof pedestals. The first row of pedestals may comprise a first racetrackpedestal. A second row of pedestals may be disposed aft of the first rowof pedestals and include a second racetrack pedestal. A third row ofpedestals may be disposed aft of the second row of pedestals and includea circular pedestal. A fourth row of pedestals may be disposed aft ofthe third row of pedestals and include a second spear pedestal. Atrailing edge cavity may be disposed aft of the forward cavity andconfigured to provide the cooling fluid to the trailing edge dischargecavity.

In various embodiments, a diameter of the first racetrack pedestal maybe equal to a diameter of the second racetrack pedestal. A diameter ofthe spear pedestal may be greater than the diameter of the firstracetrack pedestal. The first row of pedestals may have a blockage of71%.

The second row of pedestals may have a blockage of 71%. The blockage ofthe third row of pedestals may be 51%, and the blockage of the fourthrow may be 51%. A diameter of the forward pedestal may be equal to adiameter of the circular pedestal. The first spear pedestal may comprisea first depth, and the second spear pedestal may comprise a second depthless than the first depth. For example, the first depth may be 0.020inches and the second depth may be 0.012 inches.

An internally cooled engine component is also provided. The internallycooled engine component may comprise a tip flag cavity having a forwardpedestal and a first spear pedestal disposed aft of the forwardpedestal. A forward internal cavity may be configured to provide coolingfluid to the tip flag cavity. A trailing edge discharge cavity may beseparated from the tip flag cavity and include a first row of pedestals.The first row of pedestals may comprise a first racetrack pedestal andhave a blockage of 71%. A second row of pedestals may be disposed aft ofthe first row of pedestals and include a second racetrack pedestal. Thesecond row may also have a blockage of 71%. A third row of pedestals maybe disposed aft of the second row of pedestals and include a circularpedestal. The blockage of the third row may be 51%. A fourth row ofpedestals may be disposed aft of the third row of pedestals and includea second spear pedestal. The blockage of the fourth row may also be 51%.A trailing edge cavity may be disposed aft of the forward cavity andconfigured to provide the cooling fluid to the trailing edge dischargecavity.

The forgoing features and elements may be combined in variouscombinations without exclusivity, unless expressly indicated hereinotherwise. These features and elements as well as the operation of thedisclosed embodiments will become more apparent in light of thefollowing description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present disclosure is particularly pointed outand distinctly claimed in the concluding portion of the specification. Amore complete understanding of the present disclosures, however, maybest be obtained by referring to the detailed description and claimswhen considered in connection with the drawing figures, wherein likenumerals denote like elements.

FIG. 1 illustrates an exemplary gas turbine engine, in accordance withvarious embodiments;

FIG. 2 illustrates an exemplary air foil having an internal coolingpassage, in accordance with various embodiments;

FIG. 3 illustrates a cast core for casting an airfoil, in accordancewith various embodiments;

FIG. 4 illustrates the location of internal cooling features proximatethe trailing edge in an internally cooled airfoil, in accordance withvarious embodiments;

FIG. 5 illustrates the geometry and orientation of internal coolingfeatures in an internally cooled airfoil, in accordance with variousembodiments;

FIG. 6A illustrates the dimensions and orientation of internal coolingfeatures in the trailing edge of an airfoil and/or core, in accordancewith various embodiments;

FIG. 6B illustrates the geometry of a racetrack pedestal in the trailingedge of an airfoil and/or core, in accordance with various embodiments;and

FIG. 6C illustrates the geometry of a spear pedestal in the trailingedge of an airfoil and/or core, in accordance with various embodiments.

DETAILED DESCRIPTION

The detailed description of exemplary embodiments herein makes referenceto the accompanying drawings, which show exemplary embodiments by way ofillustration and their best mode. While these exemplary embodiments aredescribed in sufficient detail to enable those skilled in the art topractice the disclosures, it should be understood that other embodimentsmay be realized and that logical, chemical, and mechanical changes maybe made without departing from the spirit and scope of the disclosures.Thus, the detailed description herein is presented for purposes ofillustration only and not of limitation. For example, the steps recitedin any of the method or process descriptions may be executed in anyorder and are not necessarily limited to the order presented.Furthermore, any reference to singular includes plural embodiments, andany reference to more than one component or step may include a singularembodiment or step. Also, any reference to attached, fixed, connected orthe like may include permanent, removable, temporary, partial, fulland/or any other possible attachment option. Additionally, any referenceto without contact (or similar phrases) may also include reduced contactor minimal contact.

The present disclosure relates to casting cores and air foils havinginternal cooling cavities. Cooling features in the internal coolingcavities may have varying shapes, sizes, and orientations. Coolingfeatures included in airfoil and cores of the present disclosure includecylindrical pedestals, racetrack pedestals, and spear pedestals witheach described in greater detail below.

The cooling features disclosed herein may provide a robust airfoil tipto resist a burn-through or rub-through without starving the majority ofthe part of airflow and causing a creep rupture, before detection can bemade through borescope or other regular maintenance. Airfoils of thepresent disclosure may also back-pressure the leading edge feed and tipflag by using pedestals as described in greater detail below, so as tomaintain adequate backflow margin for cooling holes. Center discharge ofcooling flow from tip flag tends to reduce mixing losses to maintainstage efficiency, as opposed to pressure-side discharge. The centerdischarge shape of the tip flag may also maintains geometric alignmentwith remainder of trailing edge to maximize ease of manufacture of coreand ease of finishing of casting. Core thickness at the trailing edgemay be varied to balance between ease of manufacture, stage efficiency,and cooling flow utilization. Additionally, cylindrical pedestal may beaxially placed to balance with the need for drilling of cooling holesinto tip flag, and to provide ample spacing forward of spear for flowdevelopment.

Referring now to FIG. 1, an exemplary gas turbine engine 20 is shown, inaccordance with various embodiments. Gas turbine engine 20 may be atwo-spool turbofan that generally incorporates a fan section 22, acompressor section 24, a combustor section 26 and a turbine section 28.Alternative engines may include, for example, an augmentor section amongother systems or features. In operation, fan section 22 can drivecoolant (e.g., air) along a bypass-flow path B while compressor section24 can drive coolant along a core-flow path C for compression andcommunication into combustor section 26 then expansion through turbinesection 28. Although depicted as a turbofan gas turbine engine 20herein, it should be understood that the concepts described herein arenot limited to use with turbofans as the teachings may be applied toother types of turbine engines including three-spool architectures.

Gas turbine engine 20 may generally comprise a low speed spool 30 and ahigh speed spool 32 mounted for rotation about an engine centrallongitudinal axis A-A′ relative to an engine static structure 36 viaseveral bearing systems 38, 38-1, and 38-2. It should be understood thatvarious bearing systems 38 at various locations may alternatively oradditionally be provided, including for example, bearing system 38,bearing system 38-1, and bearing system 38-2.

Low speed spool 30 may generally comprise an inner shaft 40 thatinterconnects a fan 42, a low-pressure compressor 44 and a low-pressureturbine 46. Inner shaft 40 may be connected to fan 42 through a gearedarchitecture 48 that can drive fan 42 at a lower speed than low speedspool 30. Geared architecture 48 may comprise a gear assembly 60enclosed within a gear housing 62. Gear assembly 60 couples inner shaft40 to a rotating fan structure. High speed spool 32 may comprise anouter shaft 50 that interconnects a high-pressure compressor 52 andhigh-pressure turbine 54. Airfoils 55 coupled to a rotor ofhigh-pressure turbine may rotate about the engine central longitudinalaxis A-A′ or airfoils 55 coupled to a stator may be rotationally fixedabout engine central longitudinal axis A-A′.

A combustor 56 may be located between high-pressure compressor 52 andhigh-pressure turbine 54. Mid-turbine frame 57 may support one or morebearing systems 38 in turbine section 28. Inner shaft 40 and outer shaft50 may be concentric and rotate via bearing systems 38 about the enginecentral longitudinal axis A-A′, which is collinear with theirlongitudinal axes. As used herein, a “high-pressure” compressor orturbine experiences a higher pressure than a corresponding“low-pressure” compressor or turbine.

The core airflow along core-flow path C may be compressed bylow-pressure compressor 44 then high-pressure compressor 52, mixed andburned with fuel in combustor 56, then expanded over high-pressureturbine 54 and low-pressure turbine 46. Mid-turbine frame 57 includesairfoils 59, which are in the core airflow path. Turbines 46, 54rotationally drive the respective low speed spool 30 and high speedspool 32 in response to the expansion.

Gas turbine engine 20 may be, for example, a high-bypass ratio gearedaircraft engine. In various embodiments, the bypass ratio of gas turbineengine 20 may be greater than about six (6). In various embodiments, thebypass ratio of gas turbine engine 20 may be greater than ten (10). Invarious embodiments, geared architecture 48 may be an epicyclic geartrain, such as a star gear system (sun gear in meshing engagement with aplurality of star gears supported by a carrier and in meshing engagementwith a ring gear) or other gear system. Geared architecture 48 may havea gear reduction ratio of greater than about 2.3 and low-pressureturbine 46 may have a pressure ratio that is greater than about five(5). In various embodiments, the bypass ratio of gas turbine engine 20is greater than about ten (10:1). In various embodiments, the diameterof fan 42 may be significantly larger than that of the low-pressurecompressor 44. Low-pressure turbine 46 pressure ratio may be measuredprior to inlet of low-pressure turbine 46 as related to the pressure atthe outlet of low-pressure turbine 46 prior to an exhaust nozzle. Itshould be understood, however, that the above parameters are exemplaryof various embodiments of a suitable geared architecture engine and thatthe present disclosure contemplates other turbine engines includingdirect drive turbofans.

Airfoil 55 may be an internally cooled component of gas turbine engine20. Trip strips may be located in internal cooling cavities ofinternally cooled engine parts, as detailed further below. Internallycooled engine parts may be discussed in the present disclosure in termsof airfoils. However, the present disclosure applies to any internallycooled engine component (e.g., blade outer air seals, airfoil platforms,combustor liners, blades, vanes, or any other internally cooledcomponent in a gas turbine engine).

With reference to FIG. 2, an airfoil 100 is shown with cooling passage108, in accordance with various embodiments. Although an airfoil isshown, the present disclosure applies to any internally cooled part(e.g., blade outer air seals, airfoil platforms, combustor components,etc.). Airfoil 100 has a pressure side 102, a leading edge 104, and atrailing edge 106. Airfoil 100 also includes top 111 and suction side113. Pressure side 102 surface is partially cutaway to illustratecooling passages 108 defined be internal walls of airfoil 100. Hot airflowing through a gas turbine engine may first contact leading edge 104,flow along pressure side 109 and/or suction side 113, and leave airfoilat trailing edge 106.

In various embodiments, material 107 may define internal passages suchas cooling passage 108. Cooling passage 108 is oriented generally in adirection from platform 112 and attachment 114 towards top 111 (i.e., aradial direction when airfoil 100 is installed in a turbine). Airfoil100 may contain multiple cooling passages or chambers similar to coolingpassage 108 oriented in various directions with varying hydraulicdiameters. The internal cooling passages may be interconnected. Multiplecooling features may appear in the internal cooling passages, asillustrated in further detail below.

With reference to FIG. 3, a cast core 200 is shown, in accordance withvarious embodiments. Cast core 200 may be used in casting airfoil 100 todefine internal features. Cast core 200 may define features aft ofleading edge 104 and up to trailing edge 106 in airfoil 100. Cast core200 may extend beyond trailing edge 106 of airfoil 100 during thecasting process to define aft cooling openings. Cast core 200 may definecooling passage 108 of airfoil 100 and cooling features therein. In thatregard, both airfoil 100 and cast core 200 may have the cooling passagesand cooling features described herein.

The features of cast core 200 may be negatives of the cooling featuresdescribed below with respect to an airfoil 100. Stated another way,cavities, openings, passages, and the like of airfoil 100 may be definedby material in cast core 200. Cooling features and pedestals of airfoil100 that are defined by material in airfoil 100 as described herein maybe formed as passages and openings in cast core 200. Thus, the featuresdescribed below as pedestals and cooling passages may describe thestructure of an airfoil 100 and/or a cast core 200.

Cast core 200 may be placed in a mold, and the material to form acomponent (e.g., airfoil 100) may be deposited in the mold. Cast core200 may be removed from the component, leaving cavities and the desiredcooling features in the component. Airfoil 100 (as well as othercomponents using fluid turbulation) may be made from an austeniticnickel-chromium-based alloy such as that sold under the trademarkInconel® which is available from Special Metals Corporation of NewHartford, N.Y., USA, or other materials capable of withstanding exhausttemperatures.

In various embodiments, FIGS. 4-6C illustrate potential cooling featureconfigurations that may be formed on a cast core 200 or on a componentsuch as airfoil 100. When formed on a cast core 200, the coolingfeatures may appear as indentations and/or passages. When formed on acomponent (e.g., airfoil 100), the cooling feature configurations mayprotrude from and/or across an internal passage.

With reference to FIG. 4, an internal cooling configuration of anairfoil is shown as defined on a core 130 (also referred to as a castingcore) similar to or identical to cast core 200 of FIG. 3, in accordancewith various embodiments. Casting may be used to form airfoil 100 ofFIG. 2. To cast an airfoil 100 or another internally cooled componentwith a cooling passage 108, a core 130 may be formed. The core of thecomponent wall may have a negative of the internal cooling featuresdescribed herein. In that regard, pedestals inside the airfoil may bedefined by cavities 126 in core 130. Similarly, passages in the airfoilare occupied by the material 128 of core 130. In that regard, core 130may be configured as a negative of the internal passages of airfoil 100.

In various embodiments, core 130 may be placed in a mold, and thematerial to form the internally cooled component may be deposited in themold. The core 130 may be removed from the internally cooled component,leaving a cavity with the desired internal cooling features. Airfoil 100(as well as other internally cooled components) may be made from anaustenitic nickel-chromium-based alloy such as that sold under thetrademark Inconel® which is available from Special Metals Corporation ofNew Hartford, N.Y., USA, or other materials capable of withstandingexhaust temperatures.

With reference to FIGS. 2 and 4, core 130 may include a leading edge 131and a trailing edge 133 that correspond to the interior surfaces ofleading edge 104 and trailing edge 106 of FIG. 1, respectively. Tip flagcavity 134 and trailing edge discharge cavity 132 may be defined bymaterial 128 of core 130. Tip flag cavity 134 and trailing edgedischarge cavity 132 may be disposed at trailing edge 133 of core 130.Leading edge cavity 129 may feed tip flag cavity 134. Trailing edgecavity 127 may feed trailing edge discharge cavity 132. In that regard,a separate cooling channel may feed tip flag cavity 134 and trailingedge discharge cavity 132.

During operation in airfoil 100 (of FIG. 2), coolant (e.g., air) mayflow in the y direction (a radial direction with respect to axis A-A′when an airfoil is mounted to a rotor or stator) into leading edgecavity 129 and trailing edge cavity 127. The coolant may then move inthe x direction (an axial direction axis A-A′ when an airfoil is mountedto a rotor or stator) towards tip flag cavity 134 and trailing edgedischarge cavity 132, where the coolant may be ejected from airfoil 100to provide film cooling and limit back flow.

Referring now to FIG. 5, tip flag cavity 134 and trailing edge dischargecavity 132 are shown, in accordance with various embodiments. Tip flagcavity 134 of core 130 and may include pedestals of airfoil 100 (of FIG.2) defined by openings in core 130. Pedestals on tip flag cavity 134 mayhave a depth (into and out of the page) greater than the depth ofpedestals on trailing edge discharge cavity 132. For example, pedestalson tip flag cavity 134 may comprise a depth of 0.02 inches (0.5 mm) andpedestals on trailing edge discharge cavity 132 may comprise a depth of0.012 inches (0.30 mm).

In various embodiments, forward pedestal 138 and forward pedestal 139may be aligned in the y direction (i.e., a radial direction when airfoil100 is mounted to a rotor or stator). Forward pedestal 138 and forwardpedestal 139 may have the same cylindrical geometry and be disposed atan intake to tip flag cavity 134. The forward pedestals may be disposedforward of spear pedestal 170. Spear pedestal 170 may define dischargeslots 171 extending in the x direction above and below (in the ydirection) spear pedestal 170. The trailing edge 106 of airfoil 100 (ofFIG. 2) is represented by the broken line labeled A/F TE. Thus,discharge slots 171 may include an exhaust port at the intersection ofspear pedestal 170 and A/F TE.

In various embodiments, separation 135 may be defined between tip flagcavity 134 and trailing edge discharge cavity 132. In airfoil 100,separation 135 may be filled with material to define tip flag cavity 134and trailing edge discharge cavity 132. Trailing edge discharge cavity132 may include four vertical (in the y direction) rows of pedestals.Forward racetrack row 140, aft racetrack row 142, circular row 144, andspear row 146. Each row may comprise of a plurality of pedestals alignedin the y direction.

In various embodiments, forward racetrack row 140 may comprise aplurality of racetrack pedestals 160. Racetrack pedestals 160 may beelongated in the y direction with circular bottom and top contours (inthe y direction). The racetrack pedestals may be aligned in the ydirection with a shortened racetrack pedestal 162 disposed at the top(in the y direction) of forward racetrack row 140 of trailing edgedischarge cavity 132.

In various embodiments, aft racetrack row 142 may comprise a pluralityof racetrack pedestals 166. Racetrack pedestals 166 may be elongated inthe y direction with circular bottom and top contours (in the ydirection). Racetrack pedestals 166 may be aligned in the y directionwith a shortened racetrack pedestal 164 disposed at the bottom (in the ydirection) of aft racetrack row 142 of trailing edge discharge cavity132. Racetrack pedestals of forward racetrack row 140 may be staggeredwith racetrack pedestals of aft racetrack row 142 so that the openingsbetween adjacent racetrack pedestals 160 (of forward racetrack row 140)generally do not align in the x direction with the openings betweenadjacent racetrack pedestals 166 (of aft racetrack row 142).

In various embodiments, circular row 144 may include a plurality ofcircular pedestals 168 aligned in the y direction. Circular pedestals168 may have a circular geometry. Circular pedestals 168 may also bedisposed aft of forward racetrack row 140, aft of aft racetrack row 142,and forward of spear row 146. The pitch and diameter of circularpedestals 168 may be selected so that every other circular pedestal 168aligns in the x direction with an opening between adjacent racetrackpedestals 166 of aft racetrack row 142.

In various embodiments, spear row 146 may be disposed aft of circularrow 144. Spear row may comprise a row of spear pedestals 170. Spearpedestals may comprise a spear geometry having a greater width (in the ydirection) at a forward portion of the spear pedestal than at an aftportion of the spear pedestal, as described below with reference to FIG.6B. Different spear pedestals 170 in spear row 146 may includesubstantially symmetric lengths (in the x direction) and widths (in they direction). Spear pedestals in spear row 146 may have a pitch anddimensions such that each spear pedestal 170 aligns in the x directionwith an opening between adjacent circular pedestals 168.

Exemplary dimension ranges and dimensions of the pedestals in each row(with the exception of shortened racetrack pedestal 162 and shortenedracetrack pedestal 164) are provided in tables T1 and T2 below. Thedimensions in tables T1 and T2 may be varied by +/−5% and may also varyby manufacturing tolerances. Additionally, the dimensions may be scaledwith the dimensions of a core and/or airfoil. The shortened racetrackpedestals may have the same diameter and as the racetrack pedestals inthe same row with a shorter height. Height and pitch are defined in they direction. Blockage is the arithmetic equivalent to height divided bypitch and is thus the blockage percentage in the y direction.

TABLE T1 Exemplary dimensions of pedestals in each row. ROW 140 ROW 142ROW 144 ROW 146 SHAPE RACETRACK RACETRACK CIRCULAR SPEAR NUMBER 12 12 2425 DIAMETER (in) 0.025 0.025 0.026 0.026 DIAMETER (mm) 0.64 0.64 0.660.66 HEIGHT (in) 0.072 0.072 — — HEIGHT (mm) 1.8 1.8 PITCH (in) 0.1020.102 0.051 0.051 PITCH (mm) 2.59 2.59 1.30 1.30 BLOCKAGE 71% 71% 51%51%

TABLE T2 Exemplary dimension ranges of pedestals in each row. ROW 140ROW 142 ROW 144 ROW 146 SHAPE RACETRACK RACETRACK CIRCULAR SPEAR NUMBER10-14 10-14 20-30 20-31 DIAMETER (in) 0.02-0.03 0.02-0.03 0.021-0.0310.021-0.031 DIAMETER (mm) 0.51-0.76 0.51-0.76 0.53-0.79 0.53-0.79 HEIGHT(in) 0.06-0.08 0.06-0.08 — — HEIGHT (mm) 1.5-2.0 1.5-2.0 PITCH (in)0.09-0.11 0.09-0.11 0.04-0.06 0.04-0.06 PITCH (mm) 2.29-2.79 2.29-2.791.02-1.52 1.02-1.52 BLOCKAGE 60%-80% 60%-80% 40%-60% 40%-60%

Referring now to FIGS. 6A through 6C, the geometry and orientation ofpedestals disposed in tip flag cavity 134 and trailing edge dischargecavity 132 of core 130 are shown, in accordance with variousembodiments. Forward pedestal 138 and forward pedestal 139 of tip flagcavity 134 may be aligned in the y direction and have substantially thesame diameter. The center of the forward pedestals (disposed on rowcenter line 180) may be forward of the center of the forward circularportion (disposed on row center line 182) of spear pedestal 136 by adistance D₁ in the x direction. In various embodiments, distance D₁ maybe 0.165 inches (4.2 mm), 0.16-0.17 inches (4.0-4.3 mm), or 0.15-0.18inches (3.8-4.6 mm). The center of the forward circular portion(disposed on row center line 182) of spear pedestal 136 may be forwardof A/F TE by a distance D₂ in the x direction. Distance D₂ may be, forexample, 0.05 inches (1.3 mm), 0.04-0.06 inches (1.0-1.5 mm), or0.03-0.07 inches (0.76-1.8 mm).

In various embodiments, shortened racetrack pedestal 162 may be alignedwith racetrack pedestals 160 in the y direction with the center of thepedestals aligned on row center line 184. Similarly, racetrack pedestals166 may be aligned in the y direction with the center of racetrackpedestals 166 aligned on row center line 186. The center of racetrackpedestals 160 and shortened racetrack pedestals 162 may be forward ofthe center of racetrack pedestals 166 by a distance D₃ in the xdirection. Stated another way, row center line 184 may be forward of rowcenter line 186 by distance D₃. D₃ may be, for example, 0.50 inches (1.3mm), 0.45-0.55 inches (11.4-14.0 mm), or 0.4-0.6 inches (10.2-15.2 mm).

In various embodiments, circular pedestals 168 may be aligned in the ydirection with the center of circular pedestals 168 aligned on rowcenter line 188. The center of circular pedestals 168 may be aft of thecenter of racetrack pedestals 166 by a distance D₄ in the x direction.Thus, row center line 188 may be aft of row center line 186 by distanceD₄. Distance D₄ may be, for example, 0.0505 inches (1.3 mm), 0.045-0.055inches (1.1-1.4 mm), or 0.04-0.06 inches (1.0-1.5 mm).

In various embodiments, spear pedestals 170 of trailing edge dischargecavity 132 may be aligned with spear pedestal 1436 of tip flag cavity134 in the y direction. Circular pedestals 168 may be aligned in the ydirection with the center of circular pedestals 168 (disposed on rowcenter line 188) forward of the center of the forward circular portion(disposed on row center line 182) of spear pedestal 136 by a distanceD₆. D₆ may be, for example, 0.051 inches (1.3 mm), 0.045-0.055 inches(1.1-1.4 mm), or 0.04-0.06 inches (1.0-1.5 mm).

Referring now to FIGS. 6B and 6C, the geometries of racetrack pedestal160 (and other racetrack pedestals) and spear pedestals 170 are shown,in accordance with various embodiments. Racetrack pedestals may have aracetrack shape. The racetrack shape may be defined by two parallelsurfaces joined on either end by a half circular end. The half circularend may have a diameter equal to width W₁. The parallel surfaces may beseparated by width W₁ in the x direction. Width W₁ may be, for example,0.025 inches (0.64 mm). The racetrack pedestals may also comprise aheight H₁ in the y direction. Height H₁ may be, for example, 0.072inches (1.8 mm) or in a range such as 0.06-0.08 inches (1.5-2.0 mm).

In various embodiments, spear pedestals 170 may differ from racetrackpedestals 160 in geometry. Spear pedestals may comprise a forwardcircular portion 190 having a diameter H₂ and an aft parallel portion192 having a height H₃, with H₃ less than H₁. Aft parallel portion 192may be connected to forward circular portion 190 by non-parallelsurfaces 194. Aft parallel portion 192 may also comprise aft circularportion 196 having a diameter of H₃, which is the same as the height H₃of aft parallel portion 192. The values of H₂ and H₃ may be, forexample, 0.026 inches (0.66 mm) and 0.0225 inches (0.57 mm),respectively. H₂ and H₃ may also be in a range with H₂ greater than H₃such as, for example, H₂ ranging from 0.021-0.031 inches (0.53-0.79) andH₃ ranging from 0.0175-0.0275 inches (0.44-0.70 mm).

Benefits, other advantages, and solutions to problems have beendescribed herein with regard to specific embodiments. Furthermore, theconnecting lines shown in the various figures contained herein areintended to represent exemplary functional relationships and/or physicalcouplings between the various elements. It should be noted that manyalternative or additional functional relationships or physicalconnections may be present in a practical system. However, the benefits,advantages, solutions to problems, and any elements that may cause anybenefit, advantage, or solution to occur or become more pronounced arenot to be construed as critical, required, or essential features orelements of the disclosures. The scope of the disclosures is accordinglyto be limited by nothing other than the appended claims, in whichreference to an element in the singular is not intended to mean “one andonly one” unless explicitly so stated, but rather “one or more.”Moreover, where a phrase similar to “at least one of A, B, or C” is usedin the claims, it is intended that the phrase be interpreted to meanthat A alone may be present in an embodiment, B alone may be present inan embodiment, C alone may be present in an embodiment, or that anycombination of the elements A, B and C may be present in a singleembodiment; for example, A and B, A and C, B and C, or A and B and C.Different cross-hatching is used throughout the figures to denotedifferent parts but not necessarily to denote the same or differentmaterials.

Systems, methods and apparatus are provided herein. In the detaileddescription herein, references to “one embodiment”, “an embodiment”, “anexample embodiment”, etc., indicate that the embodiment described mayinclude a particular feature, structure, or characteristic, but everyembodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed. After reading the description, it will be apparent to oneskilled in the relevant art(s) how to implement the disclosure inalternative embodiments.

Furthermore, no element, component, or method step in the presentdisclosure is intended to be dedicated to the public regardless ofwhether the element, component, or method step is explicitly recited inthe claims. No claim element herein is to be construed under theprovisions of 35 U.S.C. 112(f), unless the element is expressly recitedusing the phrase “means for.” As used herein, the terms “comprises”,“comprising”, or any other variation thereof, are intended to cover anon-exclusive inclusion, such that a process, method, article, orapparatus that comprises a list of elements does not include only thoseelements but may include other elements not expressly listed or inherentto such process, method, article, or apparatus.

What is claimed is:
 1. A casting core, comprising: a tip flag cavitycomprising a forward pedestal and a first spear pedestal disposed aft ofthe forward pedestal; and a trailing edge discharge cavity separatedfrom the tip flag cavity and comprising, a first row of pedestalscomprising a first racetrack pedestal, a second row of pedestals aft ofthe first row of pedestals, the second row of pedestals comprising asecond racetrack pedestal, a third row of pedestals aft of the secondrow of pedestals, the third row of pedestals comprising a circularpedestal, and a fourth row of pedestals aft of the third row ofpedestals, the fourth row of pedestals comprising a second spearpedestal.
 2. The casting core of claim 1, wherein a diameter of thefirst racetrack pedestal is equal to a diameter of the second racetrackpedestal.
 3. The casting core of claim 2, wherein a diameter of thefirst spear pedestal is greater than the diameter of the first racetrackpedestal.
 4. The casting core of claim 3, wherein the diameter of thefirst spear pedestal is 0.026 inches.
 5. The casting core of claim 1,wherein the first row of pedestals comprises 12 racetrack pedestals, andthe fourth row of pedestals comprises 24 spear pedestals.
 6. The castingcore of claim 1, wherein a first blockage of the first row of pedestalsis 71%.
 7. The casting core of claim 6, wherein a second blockage of thesecond row of pedestals is 71%, wherein a third blockage of the thirdrow of pedestals is 51%, and wherein a fourth blockage of the fourth rowof pedestals is 51%.
 8. The casting core of claim 1, wherein a diameterof the forward pedestal is equal to a diameter of the circular pedestal.9. The casting core of claim 1, wherein a geometry of the first spearpedestal is the same as a geometry of the second spear pedestal.
 10. Thecasting core of claim 1, wherein the first row of pedestals is staggeredrelative to the second row of pedestals.
 11. The casting core of claim1, wherein the first spear pedestal comprises a first depth and thesecond spear pedestal comprises a second depth less than the firstdepth.
 12. The casting core of claim 11, wherein the first depth is0.020 inches and the second depth is 0.012 inches.
 13. An airfoil,comprising: a tip flag cavity comprising a forward pedestal and a firstspear pedestal disposed aft of the forward pedestal; a forward internalcavity configured to provide cooling fluid to the tip flag cavity; atrailing edge discharge cavity separated from the tip flag cavity andcomprising, a first row of pedestals comprising a first racetrackpedestal, a second row of pedestals aft of the first row of pedestals,the second row of pedestals comprising a second racetrack pedestal, athird row of pedestals aft of the second row of pedestals, the third rowof pedestals comprising a circular pedestal, and a fourth row ofpedestals aft of the third row of pedestals, the fourth row of pedestalscomprising a second spear pedestal; and a trailing edge cavity aft ofthe forward internal cavity and configured to provide the cooling fluidto the trailing edge discharge cavity.
 14. The airfoil of claim 13,wherein a diameter of the first racetrack pedestal is equal to adiameter of the second racetrack pedestal.
 15. The airfoil of claim 14,wherein a diameter of the first spear pedestal is greater than thediameter of the first racetrack pedestal.
 16. The airfoil of claim 13,wherein a first blockage of the first row of pedestals is 71%, wherein asecond blockage of the second row of pedestals is 71%, wherein a thirdblockage of the third row of pedestals is 51%, and wherein a fourthblockage of the fourth row of pedestals is 51%.
 17. The airfoil of claim13, wherein a diameter of the forward pedestal is equal to a diameter ofthe circular pedestal.
 18. The airfoil of claim 13, wherein the firstspear pedestal comprises a first depth and the second spear pedestalcomprises a second depth less than the first depth.
 19. The airfoil ofclaim 18, wherein the first depth is 0.020 inches and the second depthis 0.012 inches.
 20. An internally cooled engine component, comprising:a tip flag cavity comprising a forward pedestal and a first spearpedestal disposed aft of the forward pedestal; a forward internal cavityconfigured to provide cooling fluid to the tip flag cavity; a trailingedge discharge cavity separated from the tip flag cavity and comprising,a first row of pedestals comprising a first racetrack pedestal, whereina first blockage of the first row of pedestals is 71%, a second row ofpedestals aft of the first row of pedestals, the second row of pedestalscomprising a second racetrack pedestal, wherein a second blockage of thesecond row of pedestals is 71%, a third row of pedestals aft of thesecond row of pedestals, the third row of pedestals comprising acircular pedestal, wherein a third blockage of the third row ofpedestals is 51%, and a fourth row of pedestals aft of the third row ofpedestals, the fourth row of pedestals comprising a second spearpedestal, wherein a fourth blockage of the fourth row of pedestals is51%; and a trailing edge cavity aft of the forward internal cavity andconfigured to provide the cooling fluid to the trailing edge dischargecavity.